Automatic test equipment (ATE) plays a pivotal role in the manufacture of semiconductor devices. The equipment, often referred to as a tester, typically provides at-speed functional verification of semiconductor devices at the wafer level and/or packaged device level. Ensuring that individual devices work properly before implementation in a higher assembly is critical to the commercial acceptance of a device.
As semiconductor devices become more complex, the ATE required to test them often rises in sophistication and cost. Even more problematic is the trend towards system-on-chip, or SoC devices, that employ both analog and digital circuitry on a single chip. Often, such devices require a variety of instruments in the ATE to adequately perform functional test. Such instruments may include AC and DC instrumentation in the form of waveform analyzers, digitizers, RF signal generators, and others.
The instruments employed by the ATE typically reside in a testhead. The testhead serves as a somewhat mobile housing for the instrument electronics. The testhead is mobile in the sense that it may be manipulated into a position proximate the device-under-test (DUT) to minimize signal delays between the instrument electronics and the DUT. Further, the testhead typically includes a backplane for plugging in the instrument boards. In a sense, the testhead is a specialized rack or card cage.
Conventional instrument cards typically require some form of cooling. The art is replete with air cooled systems and liquid-cooled systems for use in semiconductor testheads. An example of an air cooling system is found in U.S. Pat. No. 6,208,510. Liquid cooling systems are typically employed in the form of cold plates that attach to high-power boards, or inflatable modules that compress against the hot components of a board to draw heat therefrom. One example of such a module is described in U.S. Pat. No. 5,871,042.
While the air and liquid cooling systems described above work well for their intended purposes, the entire cardcage is typically configured to support one form of cooling, or the other. This scheme was acceptable for ATE built for testing solely low performance devices (often requiring only air cooling), or ATE built for testing solely high performance devices (typically requiring liquid cooling). However, modern ATE, such as for example the J971 semiconductor tester with logic, analog and memory test instruments (manufactured by Teradyne, Inc., Agoura Hills, Calif.), provide a single platform test approach. This platform enables the testing of devices that span the performance spectrum.
What would be desirable is a testhead cooling configuration that universally supports instrument cards requiring air and/or liquid cooling, but at low cost. The hybrid cooling system of the present invention satisfies these needs.